In modern organic chemistry, palladium-catalyzed reactions, e.g. cross couplings, are broadly used as a powerful synthetic method. These processes mostly proceed through a palladium(0)/palladium(II) redox couple, which rests upon the smooth interconversion between palladium(0) and palladium(II) species. Recently, catalytic reactions involving a palladium(IV) intermediate that is generated in situ by the oxidation of a palladium(II) precursor have attracted exceptional interest in organic synthesis. Such palladium(II)/palladium(IV) catalysis can realize unprecedented transformations complementary to the conventional palladium(0)/palladium(II) catalysis because of the unique reactivity of high-valent palladium(IV) complexes. In this review article, we focus on the difunctionalization of alkenes and alkynes based on the palladium(II)/palladium(IV) catalytic cycle.